In times of war and during certain emergencies caused by natural phenomenon or accidents, the atmosphere becomes polluted with toxic chemicals. In order to be able to react to the pollutants and ameliorate their effects, it is necessary to analyze the atmosphere to detect the presence of such chemicals and their probable nature. Many efforts to solve these problems have been attempted and many are successful technically, e.g. sampling particulate fallout by mass spectrometer or atmospheric sampling by gas chromographic techniques by placing the detectors in remote areas where power requirements are severe and retrieval difficult.
Thus there is no practical means now in use for detecting toxic chemicals in the atmosphere at long range.